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How to Make an Easy Catapult for a Science Project

Catapults have been used for centuries as both a weapon and toy. They can be made easily from scrap lumber and materials found in most home workshops, and will provide hours of entertainment. Science teachers can assign students to build catapults as part of a lesson unit on force and motion. Although catapults can be fun, it is imperative to observe safety procedures and never launch an object that could cause injury.

Things You'll Need

3 thin 12-by-1-inch wood slats
8 thin 6-by-1-inch wood slats
10 small screws
Screwdriver
1 large rubber band
2 eye hooks
Wood glue
4-inch cardboard square
6-inch long metal axle from a hobby car

Instructions

Catapult Base Frame
- 1
  Take two 6-inch long wood pieces and cut each end at a 45-degree angle, creating two elongated trapezoid shapes.
- 2
  Overlap the cut edge of one cut 6-inch section with the end of a 12-inch piece to create an acute angle and screw together. Align an uncut 6-inch length of wood with the unattached end of the cut 6-inch piece to create a triangle. The uncut 6-inch section and 12-inch piece will extend past the vertices. Screw the uncut 6-inch piece to the 12-inch length and secure the uncut section to the cut piece with wood glue. Repeat this process to create the two legs of the catapult.
- 3
  Connect the two legs together by placing an uncut 6-inch piece across the front and back ends of the 12-inch pieces. Screw together to create the box frame.
- 4
  Brace the legs by screwing an uncut 6-inch section into the 6-inch brace posts where they meet the two cut sections, so that the uncut piece rests on the vertex of the cut and uncut 6-inch sections.
- 5
  Screw the last uncut 6-inch piece into the 6-inch leg posts on the opposite side of the piece attached in the previous step.
Catapult Arm
- 6
  Place the remaining 12-inch piece of wood on a flat surface. Drill a hole just big enough to insert the metal axle approximately 1/2 inch in from one end.
- 7
  Screw one eye hook into the 12-inch section, approximately 3 inches in from the end opposite the drilled hole.
- 8
  Cut and fold the 4-inch square cardboard piece into an open rectangular box to create the catapult cup. Attach to the 12-inch section directly in front of the eye hook with wood glue. The edge of the box and the open end of the hook should be touching.
- 9
  Insert the metal axle through the drilled hole so that an even amount extends out each side of the wood. Slide the metal axle between the two leg posts of the frame and secure in place with wood glue. The bar should be pressure-fit tightly between the posts. Secure with duct tape or wood glue if necessary.
Preparing to Launch
- 10
  Screw the remaining eye hook into the uncut 6-inch section of the square frame on the same side as the base of the angled pieces. Make sure the open end of the hook faces the ground.
- 11
  Connect the rubber band around the two eye hooks.
- 12
  Pull the catapult arm back down to the base. Load the cup with a light object, such as a paper wad, and let go to launch the item.

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